On Measuring Condensate Fraction in Superconductors

TL;DR

This paper discusses how magnetic neutron scattering can directly measure the condensate fraction in superconductors, especially in high-temperature ones, by analyzing off-diagonal long-range order and anisotropic order parameters.

Contribution

It demonstrates that magnetic neutron scattering can serve as a direct probe of the condensate fraction in superconductors, linking microscopic order anisotropy to measurable magnetic correlations.

Findings

Magnetic neutron scattering can measure the condensate fraction.

Recent experiments in high-temperature superconductors approach this measurement.

Spin-spin correlations are affected by the superconducting order parameter.

Abstract

An analysis of off-diagonal long-range order in superconductors shows that the spin-spin correlation function is significantly influenced by the order if the order parameter is anisotropic on a microscopic scale. Thus, magnetic neutron scattering can provide a direct measurement of the condensate fraction of a superconductor. It is also argued that recent measurements in high temperature superconductors come very close to achieving this goal.